Level 2 Applied Science

Chemical reactivity and bonding  
There are two kinds of atomic bonds covalent and ionic. They are different because of their structure and properties , covalent bonds consist of the sharing of electrons by two atoms , if two atoms differ considerably in their electro negativity   one of the atoms will lose its electron to the other atom, the outcome is that it is in a positively charged ion and negatively charged ion
Comparison chart
Covalent bonds Ionic bonds
Polarity : low High

Melting point : low High
Boiling point : low High
Occurs between : two non metals One non metal and one metal
State at room temperature: liquid or gaseous Solid
Example of a covalent bond: hydrogen (H2) Sodium chloride

Dot and cross diagram of simple ionic and covalent substances :

H20 water                         C02                               Methane

Chlorine                           hydrogen

Sodium chloride                         Magnesium Oxide

                            Simple molecular substance

  Properties of a simple molecular , giant molecular and giant ionic

One simple molecular

Co2 has a   low melting point   because the intermolecular forces of attraction are weak. Co2 is soluble in water because when it dissolves in water it interacts with surrounding H2O molecules to hydrate itself, the electronegative oxygen atoms of CO2 forms strong H-bond with H atoms of water molecules, This interaction is very strong to dissolve more and more CO2 molecules, the covalent bonds holding the molecules together are strong. Each molecule is attracted to its neighbours by only weak intermolecular forces which require little energy to overcome and hence have a low melting point. at room temperature they are usually a gas or a liquid. This is because the intermolecular forces are easily broken by a little amount of heat....